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    <p>For the 16.16 representation, the simple ternary is unlikely to be bettered speed-wise.</p> <p>And for doubles, because you need it standard/portable C, bit-fiddling of any kind will end badly. </p> <p>Even if a bit-fiddle was possible (which I doubt), you'd be relying on the binary representation of doubles. THIS (and their size) IS IMPLEMENTATION-DEPENDENT.</p> <p>Possibly you could "guess" this using sizeof(double) and then comparing the layout of various double values against their common binary representations, but I think you're on a hiding to nothing.</p> <p>The best rule is TELL THE COMPILER WHAT YOU WANT (ie ternary), and let it optimise for you.</p> <p><strong>EDIT:</strong> Humble pie time. I just tested quinmars idea (below), and it works - if you have IEEE-754 floats. This gave a speedup of about 20% on the code below. IObviously non-portable, but I think there may be a standardised way of asking your compiler if it uses IEEE754 float formats with a #IF...?</p> <pre><code> double FMIN = 3.13; double FMAX = 300.44; double FVAL[10] = {-100, 0.23, 1.24, 3.00, 3.5, 30.5, 50 ,100.22 ,200.22, 30000}; uint64 Lfmin = *(uint64 *)&amp;FMIN; uint64 Lfmax = *(uint64 *)&amp;FMAX; DWORD start = GetTickCount(); for (int j=0; j&lt;10000000; ++j) { uint64 * pfvalue = (uint64 *)&amp;FVAL[0]; for (int i=0; i&lt;10; ++i) *pfvalue++ = (*pfvalue &lt; Lfmin) ? Lfmin : (*pfvalue &gt; Lfmax) ? Lfmax : *pfvalue; } volatile DWORD hacktime = GetTickCount() - start; for (int j=0; j&lt;10000000; ++j) { double * pfvalue = &amp;FVAL[0]; for (int i=0; i&lt;10; ++i) *pfvalue++ = (*pfvalue &lt; FMIN) ? FMIN : (*pfvalue &gt; FMAX) ? FMAX : *pfvalue; } volatile DWORD normaltime = GetTickCount() - (start + hacktime); </code></pre>
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    1. COAssuming IEEE-754 for the floating point case is portable enough for my situation. Thanks for taking the time to follow up.
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    2. COThe version with `int64_t` will give wrong results when both `FMIN` and `*pfvalue` are less then zero e.g., FMIN=-1, FMAX=1, (*pfvalue)=-0.1; see my answer http://stackoverflow.com/questions/427477/fastest-way-to-clamp-a-real-fixed-floating-point-value#429391
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    3. CO@JFS Ah yes. IEE754 uses sign/magnitude encoding, not 2s complement. So comparisons with negative numbers are flawed. If FMIN and FMAX both >= zero, then you're fine (even if pfvalue is negative). If FMIN or FMAX are zero, all bets are off...
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